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Polymer processing companies, moulders, fabricators, and dedicated recycling firms can benefit from the use of liquid nitrogen in disposing of manufacturing scrap, reject materials and even finished product that a consumer may discard.
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Recyclers of rubber and plastic items must get fine particle sizes in order to allow the material to be re-formulated or re-incorporated into primary products, generally via a moulding process. Often the product being recycled consists of several dissimilar materials, such as a metal-plated or fabric-reinforced plastic. These materials must be liberated from one another so they can be separated into the individual components for recycling.
In most operations, the use of liquid nitrogen to cool a material during size reduction takes advantage of the refrigeration afforded by liquid nitrogen for one of the following reasons:
- To remove the heat of grinding to prevent melting, distortion, or discoloration of polymeric materials during processing.
- To embrittle a polymer to enable it to be size-reduced more effectively or to get selective embrittlement when two or more components exist.
- To liberate multi-component materials by using different rates of thermal expansion/contraction caused by exposure to the low temperatures of liquid nitrogen.
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The key benefits of achieving any of the above relate to significantly improved production throughput rates, improved quality due to reduction in heat history or colour distortion, finer particle sizes due to ease of particle fracture, cleaner and easier liberation and separation of mixed component scrap, and reduced specific energy consumption (grinding energy per unit of product processed) related to the size reduction step.
Air Products provides the equipment, know-how, testing and start-up services necessary for a company to optimise its size reduction operation. We provide full scale test services in our Cryo-Grind laboratory, along with the most extensive data and experience base in the Americas. Our offering generally includes a materials chiller, typically our 7 foot screw conveyor, liquid nitrogen flow controls, data acquisition system, and mill controls. |
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